Short-term but not long-term exposure to an enriched environment facilitates the extinction of aversive memory

The systemic effects of the enriched environment on the conditioned fear reaction

“…According to our hypothesis, the animals housed in the EE should extinguish the CFR faster than the animals housed in the STAND environment. This was confirmed in many experiments (Hunter, 2015;Lach et al, 2016;Hegde et al, 2017;Cavalcante et al, 2020;on others). In particular, Lach et al (2016) showed that the extinction of CFR in context occurs faster in rats housed in the EE (2 weeks) compared to the STAND group.…”

“…But in the 2nd, and especially in the 3rd trial, the freezing time of transgenic mice of the STAND group, as well as control and transgenic mice of the EE group, compared with control naive animals was significantly shorter both in the context and to presentation of CS. Cavalcante et al (2020) found that a 2-week stay in the EE caused a significant decrease in the freezing time during extinction of CFR compared to control animals, while a 4-week stay in the EE reduced the freezing time only in the last session. In our work ( Pavlova et al, 2023 ), the percentage of the freezing time decrease during extinction in the EE group in context was greater than in rats of the STAND group.…”

“…When tested after 24 h, CFR, in contrast to the unconditioned response, was approximately the same in the EE and STAND groups ( Cavalcante, 2019 ). In a subsequent work ( Cavalcante et al, 2020 ), the authors found an increase in dopaminergic neurons in the ventral tegmental area (VTA) under the influence of 2- and 4-weeks stay of animals in the EE. Coppens et al (2010) suggested that EE affects dopamine release in the mesocorticolimbic pathways.…”

“…The degree and strength of these associations depend on the magnitude and number of CS and US pairings, and the loads and presentations of environmental stimuli. With regard to the effects of EE on the CFR, many factors should be taken into account, such as the duration of staying in the EE, the age of the animal from which EE is started, features of the EE procedure (for example, its application before the onset of stress or after it); the character of the assessment tests and models used ( Clemenson et al, 2015 ; Hegde et al, 2017 ; Cavalcante, 2019 ; O’Leary et al, 2019 ; Cavalcante et al, 2020 ; Cheng S. T. et al, 2022 ) and so on. Of particular interest is the effect of EE on the developing brain.…”